Internal combustion engines utilize valves for controlling the introduction of fuel to the cylinders and for exhaustion of product of combustion from the cylinders. The valves are controlled in opening and closing by a cam shaft. The cam shaft actuates a valve lifter which in turn actuates the valve stem usually through a push rod and rocker arm. It is important for purposes of valve timing, proper sealing, and engine noise to have a proper amount of clearance in the actuating linkage for engines using mechanical or solid valve lifters. Engines using hydraulic valve lifters require a proper amount of preload in the actuating linkage. With mechanical lifters, too little clearance will result in the improper sealing of the valve itself and will materially contribute to its early failure. Too much clearance will result in improper valve timing and excessive engine noise. Improper preload on hydraulic lifters cause similar problems. In the past it has been the common practice to hand-set each engine valve (generally two for each cylinder). This method involved the operator using a feeler gage inserted in the actuating mechanism to determine when the operator had properly positioned the screw adjustment. This involved great skill of the operator in determining the feeler gage clearance. If a lock nut were involved for the adjusting screw, the operation was further complicated by the need for a third hand or some compensation for the lock nut application. The above-described manual techniques are generally considered unsatisfactory for modern engine assembly technique. Several attempts have been made to develop an automatic valve lash adjusting tool. However, to date none have been completely successful. Our invention takes full advantage of position control techniques of modern assembly line practices which will produce satisfactory tolerances and discloses a tool and method which takes unique advantage of these features.